Certain types of cameras include a light source for illuminating regions of interest that the cameras are to monitor. For example, some cameras are able to sense infrared (IR) and visible light and are correspondingly equipped with an on-camera IR and/or visible light sources for use in low-light conditions. In order for one of these cameras to properly monitor what is happening in a region of interest, the camera's image sensor should only detect light emanating from the region of interest as opposed to, for example, light from the on-camera IR or other light source that are reflected by internal components of the camera itself.